Extensional detachment faulting on the Tyrrhenian margin of the southern Apennines contractional belt (Italy)

The tectonic evolution of the Campania margin during the late Pliocene-Pleistocene is characterized by extensional deformation coeval with the opening of the Marsili oceanic basin. The initial stages of stretching are represented in the analysed area by the development of low-angle normal faults that extended the belt in the same direction as the direction of spreading recognized for the oceanic basin. Detachment faulting was accompanied by the onset of magmatic activity and by major uplifts that resulted in the accumulation of thick conglomerate successions in the half-grabens that developed in the upper plate of the extensional detachment. Deformation continued during the Mid-Pleistocene with the formation of strike-slip and normal faults trending almost parallel to the spreading direction of the Marsili basin. These faults dissected the extensional detachment and promoted counter-clockwise block rotations about vertical axes, which accommodated the ESE-directed stretching of the Marsili basin and the consequent sinistral shear imposed on the southern Apennine chain. The development of a regional detachment fault along the Tyrrhenian margin of Campania explains the complex patterns of subsidence and uplift that characterize this area during the Pleistocene and fits well within the regional geodynamic framework of the southern Tyrrhenian Sea.